Radio frequency antenna capacitively coupled to a charging coil in an implantable medical device

ABSTRACT

A design for an implantable medical device (IMD) is disclosed in which a charging coil and a short-range RF antenna in the IMD&#39;s header are physically integrated, and in which the short-range RF antenna includes intentional coupling to the charging coil. A pick-up is capacitively coupled to the charging coil in the header, such as by wrapping the pick-up at least partially around the turns of the charging coil. The charging coil is used to receive power via a magnetic inductive link at a first (preferably lower) frequency, while the combined charging coil and pick-up—together acting as the short-range RF antenna—receive and transmit short-range RF data (e.g., Bluetooth) via a short-range RF data link at a second (preferably higher) frequency. Resonance of the charging coil and short-range RF antenna can be independently tuned, and circuitry can prevent interference between them.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a non-provisional application of U.S. Provisional PatentApplication Ser. No. 62/448,271, filed Jan. 19, 2017, to which priorityis claimed, and which is incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to implantable medical devices,and more particularly to improved antenna structures for an implantablemedical device such as an implantable pulse generator.

INTRODUCTION

Implantable stimulation devices are devices that generate and deliverelectrical stimuli to body nerves and tissues for the therapy of variousbiological disorders, such as pacemakers to treat cardiac arrhythmia,defibrillators to treat cardiac fibrillation, cochlear stimulators totreat deafness, retinal stimulators to treat blindness, musclestimulators to produce coordinated limb movement, spinal cordstimulators to treat chronic pain, cortical and deep brain stimulatorsto treat motor and psychological disorders, and other neural stimulatorsto treat urinary incontinence, sleep apnea, shoulder subluxation, etc.The description that follows will generally focus on the use of theinvention within a Spinal Cord Stimulation (SCS) system, such as thatdisclosed in U.S. Pat. No. 6,516,227. However, the present invention mayfind applicability in any implantable medical device system, including aDeep Brain Stimulation (DBS) system.

As shown in FIG. 1A, an SCS system includes an Implantable PulseGenerator (IPG) 10 (Implantable Medical Device (IMD) 10 more generally),which has a biocompatible device case 12 formed of a conductive materialsuch as titanium for example. The case 12 typically holds the circuitryand power source (e.g., battery) 14 necessary for the IMD 10 tofunction, although IMDs can also be powered wirelessly without batteryassistance, as discussed further below. The IMD 10 is coupled toelectrodes 16 via one or more electrode leads 18, such that theelectrodes 16 form an electrode array 20. The electrodes 16 are carriedon a flexible body 22, which also houses the individual signal wires 24coupled to each electrode. In the illustrated embodiment, there areeight electrodes on two leads 18 for a total of sixteen electrodes 16,although the number of leads and electrodes is application specific andtherefore can vary. The proximal ends of leads 18 couple to the IMD 10using lead connectors 26, which are fixed in a non-conductive headermaterial 28 on the IMD 10, which can comprise an epoxy or silicone forexample. Although not shown, it is well known that the lead connectors26 includes contacts that communicate with stimulation circuitry in theIMD 10 through a feedthrough between the header 28 and the case, andthat also connect to contacts on the proximal ends of the leads. In thismanner, the stimulation circuitry can be controlled to providestimulation currents to any of electrodes 16, and hence a patient'stissue. In other IMDs, header 28 need not include lead connectors 26,but could include other structures (e.g., sensors) specific to theoperation or function associated with that IMD.

The IMD 10 of FIG. 1A includes two coils (more generally, antennas) atelemetry coil 30 a used to transmit/receive data along wireless link 40a to/from a transceiving coil 52 a in an external controller 50 a; and acharging coil 32 for receiving power via wireless link 42 a from atransmitting coil 62 in an external charger 60. Examples of theconstruction and operation of external controller 50 a and externalcharger 60 can be found in U.S. Patent Application Publication2015/0080982, and these devices may be integrated into a single deviceor system as discussed in U.S. Pat. Nos. 8,335,569 and 8,498,716.Wireless links 40 a and 42 a are transcutaneous and thus pass throughthe tissue of the patient when the IMD 10 is implanted.

In FIG. 1A, links 40 a and 42 a comprise near-field magnetic inductivelinks between the coils 52 a and 30 a, and 62 and 32. Generallyspeaking, the magnetic fields employed in magnetic inductive links 40 aand 42 a can comprise a frequency f1 of 10 MHz or less and cancommunicate over distances of 12 inches or less for example.

Link 42 a is used to provide power to charge the IMD 10's battery 14,which in this example is rechargeable. Alternatively, IMD 10 may also becontinuously powered by link 42 a and may therefore lack a battery. Whentransmitting power to the IMD 10 via link 42 a, an AC current atfrequency f1 is passed through the primary charging coil 62 in theexternal charger 60, which creates a magnetic field of frequency f1comprising link 42 a. This magnetic field induces an AC current in thesecondary charging coil 32 in the IMD 10, and creates an AC voltage atfrequency f1 across the coil 32. This voltage is rectified to a DCvoltage and used to either charge the battery 14 or continuously powerthe IMD 10. In an example, the magnetic field of link 42 a is set tof1=80 kHz at the transmitting coil 62, and is not modulated with data.

Data link 40 a is bi-directional, and, as a near-field magneticinduction link, is produced at telemetry coil 52 a and received attelemetry coil 32 a (or vice versa) similarly to the manner in which thecharging coil 62 in the external charger 60 communicates with thecharging coil 32 in the IMD 10. However, the magnetic field produced atcoil 52 a or 30 a is modulated with the data to be transmitted, which isthen received and demodulated at the other coil. Such modulation canoccur for example using Frequency Shift Keying (FSK), in which ‘0’ and‘1’ data bits comprise frequency-shifted values with respect to a centerfrequency of the magnetic field. Because data link 40 a is a near-fieldmagnetic inductive link, it too may comprise a frequency f1 of 10 MHz orless. In an example, the magnetic field of link 40 a can be centered atf1=125 kHz, with ‘0’ and ‘1’ data bits comprising 121 kHz and 129 kHzrespectively. Data on data link 40 a can also be modulated in othermanners, such as by amplitude or phase modulation.

In FIG. 1A, the telemetry coil 30 a is located in the IMD's header 28,while the charging coil 32 is located within the case 12. Locating thetelemetry coil 30 a in the non-conductive header 28 material, as opposedto within the conductive case 12, is beneficial because the case 12 willtend to attenuate data link 40 a, which can either render datacommunications less reliable, or require the external controller 50 aand the IMD 10 to be in closer proximity. Although not shown, the twoends of the telemetry coil 30 a would each pass though the feedthroughbetween the header 28 and the case 12, and meet with telemetry circuitryin the case 12. Telemetry coil 30 a may also reside inside the case 12,although this may require coil 30 a to have a larger area or a largernumber of turns, as described in U.S. Pat. No. 8,577,474.

FIG. 1B shows another example of an IMD 10′, and in this example thecharging coil 32 is located in the non-conductive header 28. Similarlyto the telemetry coil 30 a of FIG. 1A, the charging coil 32 of FIG. 1Bwill be largely free of attenuation caused by the conductive case 12,and hence can be made smaller or with fewer turns. Otherwise, chargingcoil 32 will operate as described earlier, and will receive via magneticinduction link 42 a a magnetic field produced by charging coil 62 in theexternal charger 60. Like telemetry coil 30 a, the two ends of thecharging coil 32 in FIG. 1B would each pass though the feedthrough andmeet with rectifier circuitry within the case 12.

IMD 10′ further includes a data antenna 30 b within the header 28,although in this example, the data antenna 30 b comprises a radiofrequency (RF) antenna instead of a magnetic-induction-based coil.Communication along data link 40 b between the data antenna 30 b and anRF antenna 52 b in an external controller 50 b is carried by far-fieldelectromagnetic waves, and preferably in accordance with well-knownshort-range wireless standards, such as Bluetooth, BLE, Zigbee, WiFi,and the Medical Implant Communication Service (MICS). The RF link 40 bpreferably comprises a frequency ranging from f2=10 MHz to 100 GHz or soand can preferably communicate over short-range distances of 100 feet orless for example (as compared to far-range RF distances as might be usedin cellular phone communication system for example). RF antenna 30 b inthe IMD 10′ (and RF antenna 52 b in the external controller 50 b) couldcomprise any number of well-known forms for an electromagnetic antenna,such as patches, slots, wires, etc., and can operate as a dipole or amonopole, and with a ground plane as necessary (not shown).

As was the case with the data telemetry coil 30 a of FIG. 1A, placingthe data antenna 30 b of FIG. 1B in the header 28 reduces concerns aboutattenuation of data communications along RF data link 40 b. However, theinventors are concerned that the design of FIG. 1B creates furtherproblems. For one, the design of FIG. 1B crowds the lead connector(s)26, the charging coil 32, and the data antenna 30 b into the limitedspace of the header 28. This can make it difficult to house all of thesecomponents while still allowing a large number of electrodes to besupported by the IMD 10. Further, this design necessarily requires thedata antenna 30 b and charging coil 32 to be in close proximity. This isconventionally not desired, as coupling between the data antenna 30 band charging coil 32 can cause them to interfere with each other'soperation. This in particular can negatively impact operation of thedata antenna 30 b, as it may be difficult to tune without resorting tothe use of complex antenna shapes that are difficult to manufacture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a prior art implantable pulse generator medical device,and in particular shows receipt of wireless power at a charging coilfrom a first near-field magnetic induction link, and receipt andtransmission of data to and from a telemetry coil along a secondnear-field magnetic induction link.

FIG. 1B shows another prior art implantable pulse generator medicaldevice, whose magnetic induction charging coil is in the device'sheader, and further including a radio frequency (RF) data antenna in theheader for receipt and transmission of data along an RF data link.

FIGS. 2A and 2B show an improved design for an implantable pulsegenerator medical device, which includes a magnetic induction chargingcoil in the device's header, and an RF antenna in the header including apick-up that is capacitively coupled to the charging coil.

FIG. 3 shows circuitry involved in tuning the charging coil and RFantenna of FIGS. 2A and 2B to resonate at low and high frequenciesrespectively.

FIGS. 4A and 4B show a different design for the RF antenna in the headerin which the pick-up that is capacitively coupled to the charging coilcomprises a wire.

DETAILED DESCRIPTION

As noted above, some IMDs like that depicted in FIG. 1B are built withboth a charging coil 32 and an RF antenna 30 b in the IMD's header 28which houses the lead connector(s) 26. Traditionally, the art has beenconcerned about coupling between these structures 32 and 30 b as one mayinterfere with the other's operation. This problem of coupling andinterference is exacerbated when the header 28 is small, or when theheader 28 includes more than one lead connector 26, as this inevitablypushes the charging coil 26 and antenna 30 b into closer proximity.

The inventors address such concerns using a design in which the chargingcoil and RF antenna in the header are physically integrated, and inwhich the RF antenna includes intentional coupling to the charging coil.Specifically, a pick-up is capacitively coupled to the charging coil inthe header by bringing the pick-up into close vicinity with the chargingcoil, such as by wrapping the pick-up at least partially around thecharging coil. In this design, the charging coil is used to receivepower via a magnetic inductive link at a first (preferably lower)frequency, while the combined charging coil and pick-up—together actingas the RF antenna—receive and transmit RF data via an RF data link at asecond (preferably higher) frequency. The pick-up is tuned to the secondfrequency by the capacitance formed between the pick-up and the chargingcoil, as well as by inductances inherent in the connections to thepick-up. The charging coil is tuned to the first frequency by acapacitor and by the inherent inductance of the charging coil. Low passfilter circuitry is included to ensure that the data signals at thesecond frequency do not pass to the power-reception rectifier.

The improved IMD 100 is shown in FIGS. 2A and 2B in planar andcross-sectional views respectively. Some of the structures depicted donot differ from those illustrated earlier in FIGS. 1A and 1B, and thusmay not be further discussed. Shown inside the case 12 of IMD 100 is aprinted circuit board (PCB 110) for integrating circuitry within thecase 12, and a battery 14. The positive (Vbat) and negative (ground;GND) connections between the battery 14 and the PCB 110 are shown, as isa connection 136 that grounds the IMD 100's conductive case 12. Thecomponents within the case 12 can be arranged in any number of ways.

Also shown in FIGS. 2A and 2B is the feedthrough 106 that containspassages 108 for signals between the case 12 and the header 28. Some ofthese signals are subsequently discussed (112, 114), but there would beother signals as well. For example, the feedthrough 106 would include apassage 108 for each of the electrode 16 signals. The cross section ofFIG. 2B shows one such electrode signal 135, which is connected to aconductive contact 103 within one of the lead connectors 26. Signal 135connects to stimulation circuitry within the case 12, and ultimately toone the electrodes 16 via one of the lead 18's signal wires 24 (FIG.1A). As is typical, the feedthrough 106 hermetically seals the interiorof the case 12: the signal wires within passages 108 are sinteredperhaps using glass ferrules, and the feedthrough 106 is welded to thecase 12 or its various portions during the IMD's construction. Thefeedthrough 106 is therefore typically shorted to the case 12 and islikewise preferably grounded.

The header 28 includes a charging coil 102 and RF antenna 105 integratedwith the charging coil 102. The charging coil 102 can be largely asdescribed earlier and will receive wireless power via magnetic inductionlink 42 a from an external charger 60 at a first frequency f1, whichagain may be 10 MHz or less. The charging coil 102 may comprise one ormore of turns of insulated wire, although individual turns aren't shown.The ends of charging coil 102 pass though the feedthrough as signals 112and are connected to operating circuitry on the PCB 110, as explainedfurther with respect to FIG. 3. Preferably the header is connected tothe case by overmolding, which process encompasses the leadconnector(s), the charging coil 102, and the RF antenna 105.

The charging coil 102 also comprises part of an RF antenna 105 used toreceive and transmit RF data along RF data link 40 b, thus allowing itto communicate with an external controller 50 b having a compliant RFcompliant antenna 52 b, as described earlier with respect to FIG. 1B. Inone example, RF data link 40 b comprises a Bluetooth link operating atf2=2.4 GHz, or more specifically within a range of frequencies close to2.4 GHz. However, the frequency used with far-field electromagnetic link40 b may be between 10 MHz and 100 GHz as noted earlier. Preferably, thefrequency of far-field RF data link 40 b (f2) is at least 100 times thefrequency of the magnetic induction power link 42 a (f1).

The RF antenna 105 includes a pick-up 104 which is capacitively coupledto the charging coil 102, and in this regard the RF antenna is formed ofboth the charging coil 102 and the pick-up 104. The pick-up 104 maycomprise a conductive sheet, for example, of foil wrapped at leastpartially around the charging coil 102, with capacitance to the chargingcoil 102 established by one or dielectric materials between the pick-up104 and the wires in the charging coil 102. Such dielectric material maycomprise the insulation of the wires within the charging coil 102,although additional dielectric materials could also be used.

As explained further below, the value of the capacitance (C1 in FIG. 3)comprises a variable used to tune operation of the RF antenna 105, andcan be adjusted by adjusting the area of the pick-up 104 relative to thecharging coil 102. When the pick-up 104 is wrapped at least partiallyaround the charging coil 102 as shown, the area (and capacitance) can beincreased or decreased by increasing or decreasing the length (x1) ofthe pick-up 104, or the extent to which it is wrapped around thecharging coil 102 (r). In one example, the pick-up 104 may wrapcompletely around the charging coil 102 and thus may comprise aconductive tube.

In the example shown, the charging coil 102 comprises straight pieces102 a and 102 b which are parallel, and which comprise long pieces ofthe oval or rectangular charging coil 102 that are parallel to a majorlength of the feedthrough 106. The pick-up 104 as shown is coupled to(e.g., wrapped around) only one of the straight pieces (e.g., 102 a) andits length x1 is also parallel to the major length of the feedthrough106. Although not shown in the figures, pick-up 104 may also couple withboth of straight pieces 102 a and 102 b, such as by being proximate to,or wrapped around, both of pieces 102 a and 102 b. There may also bemore than one pick-up 104. For example, there may be two or morepick-ups 104 around straight piece 102 a, or one or more around straightpiece 102 a and one or more around straight piece 102 b. Pick-up(s) 104may also couple to non-straight pieces of the charging coil 102 as well.

As shown in FIGS. 2A and 2B, the pick-up 104 comprises at least onesignal 114 that connects through the feedthrough 106 to the PCB 110 andRF telemetry circuitry 122 (FIG. 3) within the case 12. Preferably,signal 114 connects to one end of the pick-up 104 via a wire 132. Theother end of the pick-up 104 is preferably grounded via a wire 133 tocreate an impedance-matching transformer, as discussed further belowwith respect to FIG. 3. While this other end could be grounded at thePCB 110 through the feedthrough 106, it is preferable to ground it tothe feedthrough using a solder connection or weld 116. In anotherexample, the pick-up 104 may not be grounded, but instead may comprise asingle connection via signal 114.

In FIG. 2B, it can be seen that the integrated charging coil 102 andpick-up 104 can be positioned closer to one of the edges 28 b of header28, while the one or more lead connectors 26 can be shifted towards theopposite header edges 28 a. In this regard, header edge 28 b ispreferably placed to face outward of the patient when the IMD 100 isimplanted, so that the charging coil 102 and the RF antenna 105 will becloser to the external charger 60 and external controller 50 b withwhich they communicate, which improves communication performance. Inreality, the charging coil 102 may be thinner than how it is depicted inFIG. 2B, and pick-up 104 would not add appreciable to that thickness. Assuch, the combined charging coil 102/pick-up 104 structure may notsignificantly interfere with the lead connector(s) 26; thus, the leadconnector(s) 26 could still be centered between the header edges 28 aand 28 b. Preferably, the charging coil 102 is wound in a plane Y thatis perpendicular to a plane X of the feedthrough 106.

While the pick-up 104 is preferably a sheet or tube, it could take theform of other conductive structures that will suitably capacitivelycouple to the charging coil 102. For example, pick-up 104 could comprisea flat sheet that while close to the charging coil 102 (or close to bothpieces 102 a and 102 b) doesn't wrap around it. Or, the pick-up 104 maycomprise one or more wires. FIGS. 4A and 4B show an example of this, inwhich the pick-up 104 comprises a single wire (e.g., a continuation ofwire 132). As shown, this pick-up wire 104 runs parallel with straightpiece 102 a of the charging coil 102. However, this is not strictlynecessary, as the pick-up wire 104 may follow any portion of thecharging coil 102, including curved portions. In this example, thelinear pick-up wire 104 lacks an area with respect to the charging coil102 (compare x1 and r in FIGS. 2A and 2B), which reduces the capacitivecoupling to the charging coil 102. It therefore may be necessary toincrease the length x1 of the pick-up wire 104 to provide a suitablylarge capacitance. Note also in this example that the pick-up wire 104is only connected via signal 114, and is not grounded at its free end104′, although it could be—either by grounding to the feedthrough 106(case 12) at a connection or weld 116 (FIGS. 2A and 2B), or by passingthrough the feedthrough to ground on the PCB 110. Although not shown, apick-up wire 104 can also be coiled around the charging coil 102, as ahelix for example.

FIG. 3 shows operating circuitry for the IMD 100, which includescircuitry that interfaces with the charging coil 102 and RF antenna 105of FIGS. 2A and 2B. Operation of the circuitry when receiving power atf1 along magnetic inductive power link 42 a is discussed first, followedby receipt and transmission of data along RF link 40 b.

When receiving power via link 42 a at f1=80 kHz for example, it isuseful to tune the circuitry to AC resonate at this frequency, and suchtuning primarily occurs by adjusting the inductance of the charging coil102 (L1) and its parallel capacitor (C2), which together comprise aresonant tank circuit. As one skilled in the art will understand, thesecomponents will resonate at a frequency fres=1/SQRT(2π*L1*C2), thusallowing either L1 or C2 to be adjusted such that fres=f1. The couplingcapacitance C1 between the charging coil 102 and the pick-up 104 isrelatively small (on the order of picoFarads), and thus capacitance C1will not pass the relatively low frequency f1 at which the L1/C2 tankresonates. That is, resonance at f1 does not affect, and is not affectedby, circuitry connected to the RF telemetry circuitry 122 discussedfurther below.

The resonant energy in the L1/C2 tank is ultimately passed to rectifiercircuitry 134 via components C3-C5 and L4-L5. Capacitor C3 comprises anoptional DC blocking capacitor, and as such does not impede AC resonancefrom the L1/C2 tank from reaching the rectifier 134. The combination ofL4 and C4, and the combination of L5 and C5, each comprise low passfilters able to pass lower frequencies like f1 to the rectifier 134, butnot higher frequencies like f2 used for RF data communications, asdiscussed further below. In short, AC resonance from the L1/C2 tank atf1 is presented to the rectifier 134, which may comprise a full- orhalf-wave rectifier, or even a single diode. The rectifier produces a DCvoltage, Vdc, which can then be used to provide a recharging current,Ibat, to the battery 14. Vdc may be processed by conditioning circuitry128, which may comprise a regulator, and which may include a currentsource to set the value of Ibat.

The voltage of the battery 14, Vbat, may then in turn be used to powerthe IMD 100 at power supply node Vload, which is ultimately used topower to the IMD's load—i.e., the majority of the operating circuitryfor the IMD 100, such as its microcontroller 120, RF telemetry circuitry122, the stimulation circuitry that provide stimulation currents to theelectrodes 16 (not shown), various regulator circuits, etc. The batteryvoltage Vbat may couple to Vload through isolation circuitry 130, whichcan disconnect the battery 14 from Vload to protect either the load orthe battery under various circumstances. An example of the manner inwhich the rectifier 134, conditioning circuitry 128 and isolationcircuitry 130 can be built and operate are disclosed in U.S. PatentApplication Publication 2013/0023943.

When receiving or transmitting data at high frequencies f2, such as the2.4 GHz used for Bluetooth, the RF antenna 105 is also tuned to resonantat this higher frequency. Here, resonance is set primarily by thecharging coil 102, the capacitance C1 established between the pick-up104 and the charging coil, and inductances L2 and L3 used to couple thepick-up 104 to the RF telemetry circuitry 122 and to ground. (If an endof the pick-up 104 is not grounded as in FIGS. 4A and 4B, inductance L3would not be present). RF telemetry circuitry 122 can comprise anintegrated circuit or “chip set” operable at the frequency and with thecommunication standard necessary for data link 40 b (e.g., Bluetooth).Data to be transmitted (D(t)) can be provided by the IMD 100'smicrocontroller 120 to transmitter circuitry 126 in the RF telemetrycircuitry 122, while data received (D(r)) can be provided by receivercircuitry 124 in the RF telemetry circuitry 122 to the microcontroller120. Microcontroller 120 may via signal 121 control whether the RFtelemetry circuitry is transmitting or receiving data at a given moment.

Like capacitance C1, inductances L2 and L3 may not comprise discretecomponents, such as packaged inductors. In one example, inductances L2and L3 comprise the native inductances used in the wires 132 and 133that couple the PCB 110 to the pick-up 104 (signal 114) and that couplethe pick-up 104 to ground (at connection 116). In this sense, inductorsL2 and L3 comprise transmission lines, whose inductances can be adjustedby adjusting their lengths x2 and x3. Preferably, lengths x2 and x3 areon the order of millimeters, as wires of these lengths will haveinductances on the order of nanoHenries. Considering again the aboveresonance equation, and assuming again that the capacitance C1 betweenthe pick-up 104 and the charging coil 102 is on the order of picoFarads,the RF antenna 105 can be made to resonate at f2=2.4 GHz, and thus willbe able to both transmit and receive Bluetooth data in this example.When operating at high frequency f2, the side of capacitance C1 oppositethe pick-up 104 couples to ground through the charging coil 102 andcapacitors C4 and C5, which capacitors at high frequencies willessentially act as shorts to ground, thus establishing two parallelmonopoles. In this regard, the charging coil 102 also comprises part ofthe equivalent circuit when operating at high frequencies, although athigh frequencies the charging coil 102 will operate as a distributedcomponent and will effectively act as a transmission line whose physicallength will influence resonance.

In FIGS. 3, L2 and L3 are shown not as they connect to the pick-up 104,but instead as an equivalent circuit, recognizing that the inductance ofthe pick-up 104 is negligible. Notice that L2 and L3 effectively form animpedance-matching transformer. Adjusting their inductances (e.g., theirlengths x2 and x3) allows for setting the AC voltage V2 at theinput/output of the RF telemetry circuitry 122 relative to the ACvoltage V1 at the pick-up 104 in accordance with the equation(V1/(V1+V2))²=(x2/(x2+x3))².

Even though the charging coil 102 and pick-up 104 are illustrated asbeing capacitive coupled (C1), they could be coupled in other manners.For example, they could be inductively coupled, or distributivelycoupled which would be especially useful when used with a large chargingcoil 102. Despite coupling between the charging coil 102 and pick-up104, that the circuitry can largely be independently tuned for resonanceat low frequencies (f1; by adjusting L1, C2) and for resonance at highfrequencies (f2; by adjusting C1, L2, and L3). Those of skill in the artof antenna design will however recognize that parasitic effects maystill be present, and therefore some amount of experimentation may berequired to optimize resonance of the circuitry at low and highfrequencies f1 and f2.

While the disclosed charging/data antenna structures have been describedas useful with particularized links 40 b and 42 a, the physics involvedin these links could be varied. For example, while IMD charging link 42a is preferably a near-field magnetic induction link, it could alsocomprise a link operable with far-field electromagnetic waves. See,e.g., U.S. Pat. No. 9,044,616 (describing an IMD chargeable withfar-field electromagnetic waves). Similarly, data link 40 b, whilepreferably a short-range RF link (e.g., 100 feet or less), couldcomprise a far-range RF link operable with far-field electromagneticwaves, or even a near-field magnetic induction link.

While the disclosed charging coil 102 and RF antenna 105 comprising thecapacitively-coupled pick-up 104 and charging coil 102 have beendescribed as residing within an IMD's header 28, this is not strictlynecessary. For example, these structures could also reside within anIMD's case 12, even though the case if conductive would attenuatereceipt of power and data communication to some degree. These structurescould also reside in any non-conductive material, whether in a cavitywithin such material, or molded into the material. Finally, thedisclosed charging coil 102 and RF antenna 105 could be used in productsother than implantable medical devices.

Although particular embodiments of the present invention have been shownand described, it should be understood that the above discussion is notintended to limit the present invention to these embodiments. It will beobvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present invention. Thus, the present invention is intended to coveralternatives, modifications, and equivalents that may fall within thespirit and scope of the present invention as defined by the claims.

What is claimed is:
 1. An implantable medical device, comprising: acharging coil configured to wirelessly receive power for the implantablemedical device via a power link at a first frequency; and a pick-upcapacitively coupled to the charging coil, wherein the pick-up and thecharging coil comprise a Radio Frequency (RF) antenna configured toresonate to wirelessly transmit and receive data via an RF link at asecond frequency.
 2. The implantable medical device of claim 1, furthercomprising a case containing operating circuitry for the implantablemedical device.
 3. The implantable medical device of claim 2, furthercomprising a non-conductive material connected to the case, wherein thecharging coil and the pick-up are within the non-conductive material. 4.The implantable medical device of claim 3, further comprising at leastone lead connector within the non-conductive material, wherein the atleast one lead connector is configured to receive a medical lead used toprovide therapy to a patient.
 5. The implantable medical device of claim4, wherein the non-conductive material is overmolded onto the case andencompasses the at least one lead connector, the charging coil, and thepick-up.
 6. The implantable medical device of claim 2, wherein theoperating circuitry comprises power rectification circuitry.
 7. Theimplantable medical device of claim 6, further comprising a rechargeablebattery within the case, wherein the power rectification circuitry isconfigured to recharge the rechargeable battery using the power receivedat the charging coil via the power link.
 8. The implantable medicaldevice of claim 6, wherein the operating circuitry further comprises lowpass filter circuitry between the charging coil and the powerrectification circuity, wherein the low pass filter circuitry isconfigured to pass power received at the first frequency, and whereinthe low pass filter circuitry is configured to not pass data at thesecond frequency.
 9. The implantable medical device of claim 2, whereinthe pick-up is connected to RF telemetry circuitry configured torespectively generate and process the transmitted and received data. 10.The implantable medical device of claim 3, further comprising afeedthrough between the non-conductive material and the case.
 11. Theimplantable medical device of claim 10, wherein the feedthrough has amajor length, wherein the pick-up has a length parallel to the majorlength of the feedthrough.
 12. The implantable medical device of claim10, wherein the feedthrough is located in a first plane, and wherein thecharging coil is located in a second plane perpendicular to the firstplane.
 13. The implantable medical device of claim 10, wherein thefeedthrough comprises passages to couple ends of the charging coil tothe operating circuitry, and to pass at least a first signal wirebetween the operating circuitry and the pick-up.
 14. The implantablemedical device of claim 1, wherein the charging coil and the pick-up arewithin a non-conductive material.
 15. The implantable medical device ofclaim 1, wherein the pick-up comprises a conductive sheet.
 16. Theimplantable medical device of claim 15, wherein the conductive sheet iswrapped at least partially around a piece of the charging coil.
 17. Theimplantable medical device of claim 1, wherein the pick-up comprises awire.
 18. The implantable medical device of claim 1, wherein the RFantenna comprises a far-field RF antenna, and wherein the RF linkcomprises a far-field RF link comprising electromagnetic waves in whichthe second frequency ranges from 10 MHz to 100 GHz.
 19. The implantablemedical device of claim 18, wherein the RF antenna comprises ashort-range RF antenna, and wherein the RF link comprises a short-rangeRF link with a communication distance of 100 feet or less.
 20. Theimplantable medical device of claim 1, wherein the power link comprisesa near-field magnetic induction link.
 21. The implantable medical deviceof claim 1, wherein the second frequency is higher than the firstfrequency.
 22. The implantable medical device of claim 21, wherein thesecond frequency is at least 100 times higher than the first frequency.